Method for pre-stressing armored well logging cable

ABSTRACT

The particular embodiment described herein as illustrative of the invention relates to method and apparatus for use in manufacturing pre-stressed well logging cables. By use of the present invention, the occurrence of undesirable permanent stretch while the cable is in use will be reduced. The method includes the steps of heating the finished cable to a point substantially less than the melting point of the visco elastic, thermoplastic inner conductor insulators but high enough to make the insulators very pliable, and placing the cable under tension sufficient to deform the conductor insulators. The cable is then cooled to a normal ambient temperature while still under tension. Apparatus capable of performing this method is also disclosed.

United States Patent Whitfill, Jr. 1 Jan. 8, 11974 [54] METHOD FORPRE-STRESSING ARMORED 3,113,934 12/1963 Grosman 264/174 X WELL LOGGINGCABLE 2,770,014 11/1956 Nordlin 264/280 X [751 inventor: qweiiliam A.Whitflll, Jr., Houston, Primary Examiner Robert F White AssistantExaminer-Richard R Kucia [73] Assignee: Schlumberger TechnologyAttorney-David L. Moseley, Stewart F. Moore and Corporation, New York,NY. William R. Sherman [22] Filed: Mar. 16, 1971 Appl. No.: 124,689

Related U.S. Application Data Continuation of Ser. No. 809,357, March21, 1969, abandoned.

US. Cl. 174/108, 174/118, 264/27, 264/103, 264/231 Int. CL... 829d23/12, H0lb 13/00, l-lOlb 7/22 Field of Search 264/103, 229-231,264/174, 280, 27; 174/108 [5 7] ABSTRAQT The particular embodimentdescribed herein as illustrative of the invention relates to method andapparatus for use in manufacturing pre-stressed well logging cables. Byuse of the present invention, the occurrence of undesirable permanentstretch while the cable is in use will be reduced. The method includesthe steps of heating, the finished cable to a point substantially lessthan the melting point of the visco elastic, thermoplastic innerconductor insulators but high enough to make the insulators verypliable, and placing the cable under tension sufficient to deform theconductor insulators. The cable is then cooled to a normal ambienttemperature while still under tension. Apparatus capable of performingthis method is also disclosed.

9 Claims, 5 Drawing Figures COOL 38 i n PATENTEUJAH 8 19% SEE? 10? 2FIG. I

F/GZ

William A. Wh/tf/ll,

NVVENTOR BY a/aafi/abl A TTOR/VEY METHGD FOR PRE-STRESSING ARMORED WELLLOGGING CABLE BACKGROUND OF THE lNVENTlON This application is acontinuation of my copending application Ser. No. 809,357 filed Mar. 21,1969, and now abandoned.

This invention relates to the manufacture of cable and more particularlyto the manufacture of high quality armored well logging cable which ispre-stressed to minimize permanent stretch.

Armored cables used in well logging generally serve a dual purpose.First, the cable provides electrical communication with the well loggingtool. Secondly, and equally important, the cable provides a means ofcontinuously measuring the depth of the well logging tool while it isbeing raised and lowered in the borehole.

It will be appreciated that under normal use of a logging cable, it willexpand and contract due to the high temperature and to pressure forcespresent in the well bore and acting on the cable. However, such thermalexpansion and contraction of the cable may be taken into account indepth calibration from the known properties of the cable materials. Forthe cable to be useful in measuring the depth of the logging tool,however, the so-called permanent stretch of the cable must be kept at aminimum since this type of stretch is not predictable in nature. Thepermanent stretch in a cable may be defined as that change in length ofthe cable measured at a reference temperature and tension, after thecable has been subjected to a heat and tension cycle, such as would beencountered in a well bore. This stretch may generally be attributed toimperfections in the cables construction. These imperfections causespaces or interstices to be present in the cables interior. When thecable is placed under tension the interstices provide room for expansionand deformation to take place in the cable interior, thus allowingpermanent stretch.

it has long been recognized that permanent stretch in a well loggingcable is an undesirable feature. To solve this problem, prior artmethods of pre-stressing logging cables have been used but with varyingdegrees of success. Permanent stretch caused by torsional unbalance ofthe cable has, for example, been compensated for by the method ofpre-stressing disclosed in U. 5. Pat. No. 3,137,988 which is assigned tothe assignee of the present invention. Hot pro-stressing cable usingrubber in sulation material is disclosed in U. S. Pat. 3,153,696 whichis assigned to the assignee of the present invention also. However, dueto the requirements of more modern and sophisticated electroniccircuitry in use in well logging services, increased requirements areplaced upon the electrical characteristics of the cable. For thisreason, the prior art cables which utilized rubber insulated electricalconductors have been to a large extent replaced with logging cablesutilizing plastic insulated conductors of thermoplastic insulationmaterials such as ethylene-propylene polymer or the like. While suchthermoplastic insulating materials have improved electricalcharacteristics, unfortunately such materials have a property which canbe called a memory" with respect to shape. That is to say, suchmaterials will tend to regain their original shape after heating anddeforming. This property may also be referred to as that ofviscoelasticity. What is intended herein when using this term with respect tothe thermoplastic material (such as polyethelene) used in well loggingcable conductor insulators is a shape memory which is not set but whichmay be altered by the application of a heating, deforming, and coolingsequence such as that which will be subsequently described. 0n the otherhand, the prior art insulating materials such as vulcanized rubber didnot have this shape memory and cables containing conductors insulatedwith such prior art materials could be pre-stressed by simultaneouslyheating and applying tension, as disclosed in the abovementioned patent,without encountering the difficulties of having the conductor insulatorslater tend to return to their original shape.

Accordingly, it is an object of the present invention to provide new andimproved methods for pro-stressing well logging cables with conductorinsulation having a plastic shape memory, or the property of viscoelasticity, the present invention avoiding the difficulties of prior arttechniques.

A further object of the present invention is to provide an improvedmethod for pie-stressing cable continuously during its manufacture byutilizing a heating and cooling cycle designed to alter the plasticmemory of the thermoplastic insulation material surrounding theconductors.

A still further object of the present invention is to provide a novelmethod for stabilizing the length of electrical well logging cablesduring the manufacture of the cable in order to minimize changes inlength of the cable during use in a well logging environment.

Briefly, in accordance with the objects of the present invention, anovel method for pro-stressing cable utiliz ing plastic insulatedconductors for use in oil well log ging services is provided. lnorder toprevent undesirable permanent stretch in a well logging cable, themethod of the present invention provides steps for tensioning the cableduring its manufacture and after the final layers of armor are woundabout the core of the cable. The tensioning step lengthens the cable andapplies inward radial pressure on the cable core to com pact the core.While this inward radial pressure is being applied, the cable is heatedto a degree where the insulators in the cable core are readilydeformable but not flowing. The pressure supplied by the tension forcesthe outer armored layers of the cable radially inward then deforms theinsulators on the inner conductors in such a manner that all theinterior interstices between the cable conductors are filled by thedeformed insulating layers. The cable is then cooled while the tensionis maintained. The cooling process alters the plastic memory of theconductor insulators and forces them to retain their deformed shape,thus the insulators will remain in their deformed state when the tensionis removed. This process may be referred to as compacting the centralcable core.

The novel features of the present invention are set forth withparticularity in the appended claims. The operation, together withfurther objects and advantages of the invention may be best understoodby way of illustration and example of certain embodiments when taken inconjunction with the accompanying drawings.

BRlEF DES-ClRlFTlON OF THE DRAWINGS FlG. l is a sectional view of acable of the present invention;

H6. 2 is a schematic diagram showing a production line for producing thecable of the present invention;

FIG. 3 is an enlarged cross-section view showing the construction of thecable of the present invention prior to the pre-stressing process;

FIG. 4 is an enlarged cross-section view showing the construction of thecable of the present invention after prestressing; and

FIG. 5 is a more detailed schematic drawing showing the novelpre-stressing apparatus used in the present invention for altering theplastic memory of the cable materials.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1, and 3the overall construction of a seven conductor well logging cable inaccordance with the principles of the present invention is shown. Thecenter conductor 11 is surrounded by an extruded insulation made of athermoplastic ethylene-propylene polymer. Although not all types ofpolypropylene have the property of visco elasticity it will beunderstood herein that the materials used in well logging cableconductor insulators do possess this property and that the pre-stressingsteps to be described hereafter act to alter the shape memory of suchconductor insulators. Outer conductors 14 are of the same constructionas the center conductor and also have ethylene-propylene polymerinsulator layers 13. Filler layer 12 is a cured, solid material appliedsimultaneously as the outer conductors are cabled about the innerconductor. This material is applied as a slurry which is picked up asthe conductors are cabled. This material may be DPR (depolymerizedrubber) or the like and is self curing and sets into a solid state.Cotton yarn 16 or the like is simultaneously wound about the inner coreto partially fill the external interstices 51 between the outerconductors l4. Overlying this subassembly is a layer which may be aDacron tape material orthe like, wrapped about the inner core in orderto facilitate handling during production. The inner construction of thecable is surrounded by two layers of armor l7 and 18. These armor wirelayers are cablewound with opposite lays, i.e., one layer has aleft-hand lay, the other a right-hand lay, and differing pitches in themanner disclosed in U. S. Pat. No. 3,137,988, in order to provide atorque-balance cable. These armor layers perform the load bearingfunction of the cable and further serve to protect the inner core.

Referring still to FIG. 3, a cross-sectional view of the cable of FIG. 1is shown to illustrate the symmetrical distribution of the cableconductors prior to the application of the pre-stressing method of thepresent invention. The conductors in the cable core being ofa roundcross section leave gaps or interstices 51 between the conductors. Whenlongitudinal tension is applied to the cable, the outer armor, which isspiral wrapped as indicated by its elliptical cross section in FIG. 3,tends to unwind, and hence exerts inward radial forces upon the cablecore and forces the insulators of the conductors to deform and expandinto the interstices of the cable. This may be further appreciated byreference to FIG. 4 which shows a cross section of the cable when placedunder tension. The straightening out of the armor, as may be appreciatedby the decreased eccentricity of the elliptical cross section of thearmor strands, exerts an inward radial force on the cable core. Thisforce compresses the core, deforming the conductor insulators l0 and 13so as to fill all remaining interstices 51.

Even though filler material 12 is applied during the manufacturingprocess, this does not prevent the insulators from deforming and fillingup the interstices because the filler material does not completely fillall the interstices in the cable and, moreover, the filler iscompressible.

Prior art cables utilizing rubber insulators over the conductors couldbe pre-stressed by heating the cable to the point where the rubber wasreadily deformable and then placing the cable under tension. This woulddeform the rubber to fill the internal interstices and, since the rubbermaterial did not have a shape memory it would retain the deformed shapewhen the tension was released. The thermoplastic insulation ofethylenepropylene polymer or the like in use on the improved loggingcables, however, have this memory characteristic or property of viscoelasticity which, if the same prestressing technique as utilized withthe rubber covered conductors were used, would cause the conductorinsulator ultimately to reassume its circular cross section upon releaseof the tension from the cable.

In a typical well logging application, the cable passes through aheating and cooling cycle while under tension. That is, when the cableis lowered into the well, it is gradually heated under tension, i.e.,the weight of the sonde, and when it is removed from the well, it isgradually cooled under tension. The tension placed on the cable by thelogging sonde can cause the outer armor to exert an inward radial force,thus deforming the cable conductors as the logging sonde is lowered intothe well. However, as the sonde is withdrawn from the well, theinsulators of the conductors are held in their deformed state while thecable is cooled. This cooling of the cable under tension can have theeffect of altering the memory cycle of the ethylene-propylene polymerouter conductor insulators and, hence, the conductor insulators wouldretain their deformed state. When this happens in the borehole, ofcourse, undesirable permanent stretch is introduced into the cable asthe inner diameter of the central cable constructionis reduced.Consequently the cable is no longer calibrated as to length.

The recognition that this effect happens in the use of the cables inwell logging has led to the method and apparatus for manufacture of thecable of the present invention which duplicates the worst possibleconditions to be encountered in well bore use, and hence, prestressesthe cable so as to avoid undesirable permanent stretch when the cable islater used in the logging operation.

Turning now to FIG. 2, a production line for producing the armored cablefor well logging operations and utilizing the pre-stressing method ofthe present invention is illustrated schematically. The single centerconductor is fed from the supply spool 31 through a cabling machine 32which cable-wraps the other insulated conductors furnished from supplyspools 41 about the center conductor in the symmetric configurationshown in FIG. 3. Simultaneously, the cotton filler yarn 16 is wrapped topartially fill the external interstices between the outer conductors. Asthe cable progresses through the cabling machine 32 the conductor passesthrough a slurry of filler material 12. The conductor 13 and cottonfillers 16 pick up some of this slurry and it thus becomes impregnatedinto the structure of the cable core. Filler material 12 may be a selfcuring filler such as depolymerized rubber (D.P.R.) or the like. The

central cable core is then wrapped with a Dacron tape layer l5 bywrapping apparatus 35.

At this point, the cable core is complete and the cable is ready toreceive the outer layers of armor wires. The central cable core passesthrough a first armor layer wrapping machine 36 and then through asecond armor layer applicator 37. These machines wrap armor wires fromsupply spools 42 and 43 with opposite lays and differing pitches toprovide a torque balanced construction. Now the cable construction iscomplete and the prestressing process to eliminate the undesirablepermanent stretch is commenced.

Tension is applied to the cable between points A and B which may be thepoints where the cable enters or exits from motor-driven capstans or thelike, and electrical current is passed through the outer armor of thecable between points A and C to heat the central core to a temperatureof approximately 250 F. This temperature is below the melting point ofthe conductor insulators, however, it will cause the visco elasticethylenepropylene polymer conductor insulator material to be readilydeformable. The tension in the cable causes the outer armor to pressradially inward on the cable core thus deforming the conductorinsulators in the manner illustrated in FIG. 4 into a hexagonal or otherirregular shape so as to fill any interstices 51 remaining between thecable conductors completely. While the cable is still under the tensionbetween points A and B, it is passed through a cooling trough 38 whichis long enough to contain the cable for a length of time suiticient toreduce the temperature to approximately 70F, thus altering the plasticmemory of the ethylenepropylene polymer conductor insulators so thatthey will not return to their formerly rounded shape. Finally, the cableis taken up on a takeup reel 3d (shown partially obscured) and is readyfor use.

Referring now to FIG. 5, an apparatus for prestressing a cable and foraltering the plastic memory of the thermoplastic insulator is shown inmore detail but still schematically. Finished armored cable 86 is paidout from a source such as a supply spool 7i or from a cable constructionline in a continuous manner. The cable passes several turns around acapstan 72 and then passes several turns around another capstan 73..From capstan 73, the cable is passed several turns around capstan "74.Motor 85 drives the capstan 74 and turns capstans 72 and 73. Capstans72, 73 and '74 are provided with adjustable friction drag brakes 75.Motor 32 drives capstan 31 and provides the main part of the motiveforce to move the cable through the system. After leaving capstan 74,the cable passes over sheaves rs and 77 and parallel to the uppersupporting member 87 of the apparatus. Heater current is supplied byheater current supply 78 through commutators 38 to sheaves 76 and 77.The current is coupled to the cable armor by conduction to provide aheating source for bringing the temperature of the conductor insulatorsinterior to the cable up to a temperature of about 250? After the cablepasses around sheave 77, it is routed through cooling trough 90 and oversheave 79 and maltes several turns each around capstans 80 and 821. Thecable is then taken up on take-up reel 83, which is powered by motor 8-3.

The operation of the system may be described as follows. Motors 82, 84and 85, which may be tied together with a servo type control system tomaintain a sustained rate of output from the system, power the cablethrough the system. Motor which furnishes most of the motive force isdriven at a faster rate than motor 85. This, coupled with the brakingaction of the variable friction drag brakes 75 on capstans 72, 733 and74, furnishes the degree of tension necessary to compress the inner coreof the cable and to deform the inner conductors. This tension may forexample, be approximately 6,000 lbs. which is less than two thirds ofthe breaking strength of the cable but greater than tension encounteredin normal well logging usage. The cable may be thought of as enteringthe pro-stressing system at capstan '72 which corresponds to point A inthe diagram of MG. 2. The cable is under this tension from capstan 72until it leaves capstan which corresponds to point B of HG. 2. While thecable is under tension, it first passes between sheaves 7s and 77 wherethe heating current is applied to the outer armor layers to bring thetemperature of the inner core to the desired point of deformation butbelow the melting point (325?) of the ethylene-propylene polymerinsulating material of the inner conductors. At this point, due to thetension in the cable, the inner core is compressed and the conductorinsulators are deformed to completely fill the interstices within thecable core. Then the cable is cooled in the cooling trough 9b whichcontains a suitable coolant, such as water or the like, while the cableis still under tension and the conductor insulator deformed. Cooling thecable while it remains under tension in cooling trough 9b thereby altersthe plastic memory of the conductor insulator material and provides acable core in a pre-stressed condition. That is the plastic memory ofthe conductor insulator is now changed so that the insulators tend toremain in their deformed shape rather than return to their previouslyround state when the tension is released. The cable then passes oversheave 79 and out the system of capstans 3b and El onto the take-up reel$33.

It will be appreciated from the foregoing discussion that while this isa continuous process which is performed during the manufacture of thecable for pre stressing, the process simulates the actual conditionswhich will be encountered by logging cable in the well bore at least tothe degree of securing the necessary pre-stressing conditions to avoidpermanent stretch in the cable when itis utilized in the well here.

Summarizing, the method steps involved in the prestressing process maybe outlined as follows:

1. Tensioning a cable to be pro-stressed. to approximately 6,000 lbs. atapproximately lF.

2. Heating the tensioned cable to approximately 250% to deform the innerconductor insulators of the cable.

3. Cooling the cable to approximately 70F while the conductors are stillin their deformed state to alter the plastic memory of the conductorinsulators. 4. Relaxing the tension in the cable and spooling it up on atake-up reel.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention and its broader aspects; and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

in the method of manufacturing a well logging cable comprising a centralcable core, a covering layer of flexible tape material wound about saidcentral core, an inner armor layer of closely spaced helically woundmetallic strands disposed about said central core and said coveringlayer, and an outer armor layer of closely spaced helically woundmetallic strands disposed about said inner armor and inclined oppositeto said inner strands, said central cable core containing a plurality ofouter conductors disposed around a central conductor, each saidconductor being insulated with a coating of viscoelastic thermoplasticinsulation material,

the improvement whereby said central cable core is permanentlycompacted, substantially eliminating the interstices between adjacentinsulated conductors thereof, and the well logging cable is thereby madeto exhibit essentially no irreversible permanent stretch when subjectedto the tensions and temperature cycles encountered in logging a well,which improvement comprises the steps of: Taking the cable, after thearmor layers have been wrapped around said central core, and passingsaid cable between a payout means and a takeup means under asubstantially constant tension less than about two-thirds the breakingstrength of said cable but sufficient to cause said armor layers toelongate and thereby supply inward radial compressive forces on saidcentral cable core; as said cable passes between said payout and saidtakeup means, heating a portion of the thustensioned cable to a. degreesufficient to cause said thermoplastic insulation material in suchheated portion to deform under said inward radial compressive forces andsubstantially to fill the previously existing interstices between theinsulated conductors of said central cable core; and before the heatedportion of the cable reaches the takeup means and while maintaining saidtension, cooling said portion to ambient conditions.

2. The method of claim 1 wherein the step of heating the tensioned cableis performed by passing an electric current through the outer armorlayers comprising a portion of the structure of the cable.

3. The method of claim 1 wherein the step of cooling the tensioned cableis performed by continuously passing the tensioned cable through atrough containing a coolant material.

4. In the method of manufacturing a well logging cable comprising acentral cable core, a covering layer of flexible tape material woundabout said central core, an inner armor layer of closely spacedhelically wound metallic strands disposed about said central core andsaid covering layer, and an outer armor layer of closely spacedhelically wound metallic strands disposed about said inner armor andinclined opposite to said inner strands, said central cable corecontaining a plurality of substantially cylindrical conductors, eachsaid conductor being insulated with a substantially uniform thickness ofthermoplastic ethylene-propylene polymer insulation material,

the improvement whereby said central cable core is permanentlycompacted, substantially eliminating the interstices between adjacentinsulated conductors thereof, and the well logging cable is thereby madeto exhibit essentially no irreversible permanent stretch when subjectedto the tensions and temperature cycles encountered in logging a well,which improvement comprises the steps of: passing the cable between apayout means and a takeup means under a substantially constant tensionless than about two-thirds the breaking strength of said cable butsufficient to cause said armor layers to elongate and thereby supplyinward radial compressive forces on said central cable core; heating aportion of the thus-tensioned cable, as it passes bween said payout andsaid takeup means, to a temperature below the melting point of saidethylene-propylene polymer but suff cient to cause saidethylene-propylene polymer to deform under said inward radialcompressive forces and to fill substantially the previously existinginterstices between the insulated conductors of said central cable core;and thereafter, while maintaining said tension and before said heatedportion reaches said takeup means, passing said heated cable portionthrough a cooling trough long enough to reduce the cable temperature toambient conditions.

5. The method of claim 4 wherein the tension between the payout meansand the takeup means is maintained at approximately 6,000 pounds.

6. The method of claim 4 wherein the tensioned cable is heated bypassing an electric current through the outer armor layers of said cableas the cable passes from said payout means to a point C intermediatebetween said payout means and said takeup means.

7. The method of claim 6 wherein the cable is heated sufficiently toraise the temperature of the conductor insulation to approximately 250F.

8. The method of claim 7 wherein the cable is cooled by passing saidcable through a trough of coolant material located between intermediatepoint C and said takeup means and long enough to lower the temperatureof the conductor insulation of said cable to approximately F while saidcable moves through said trough.

9. A well logging cable manufactured by the method of claim 8.

1. In the method of manufacturing a well logging cable comprising acentral cable core, a covering layer of flexible tape material woundabout said central core, an inner armor layer of closely spacedhelically wound metallic strands disposed about said central core andsaid covering layer, and an outer armor layer of closely spacedhelically wound metallic strands disposed about said inner armor andinclined opposite to said inner strands, said central cable corecontaining a plurality of outer conductors disposed around a centralconductor, each said conductor being insulated with a coating ofviscoelastic thermoplastic insulation material, the improvement wherebysaid central cable core is permanently compacted, substantiallyeliminating the interstices between adjacent insulated conductorsthereof, and the well logging cable is thereby made to exhibitessentially no irreversible permanent stretch when subjected to thetensions and temperature cycles encountered in logging a well, whichimprovement comprises the steps of: Taking the cable, after the armorlayers have been wrapped around said central core, and passing saidcable between a payout means and a takeup means under a substantiallyconstant tension less than about two-thirds the breaking strength ofsaid cable but sufficient to cause said armor layers to elongate andthereby supply inward radial compressive forces on said central cablecore; as said cable passes between said payout and said takeup means,heating a portion of the thus-tensioned cable to a degree sufficient tocause said thermoplastic insulation material in such heated portion todeform under said inward radial compressive forces and substanTially tofill the previously existing interstices between the insulatedconductors of said central cable core; and before the heated portion ofthe cable reaches the takeup means and while maintaining said tension,cooling said portion to ambient conditions.
 2. The method of claim 1wherein the step of heating the tensioned cable is performed by passingan electric current through the outer armor layers comprising a portionof the structure of the cable.
 3. The method of claim 1 wherein the stepof cooling the tensioned cable is performed by continuously passing thetensioned cable through a trough containing a coolant material.
 4. Inthe method of manufacturing a well logging cable comprising a centralcable core, a covering layer of flexible tape material wound about saidcentral core, an inner armor layer of closely spaced helically woundmetallic strands disposed about said central core and said coveringlayer, and an outer armor layer of closely spaced helically woundmetallic strands disposed about said inner armor and inclined oppositeto said inner strands, said central cable core containing a plurality ofsubstantially cylindrical conductors, each said conductor beinginsulated with a substantially uniform thickness of thermoplasticethylene-propylene polymer insulation material, the improvement wherebysaid central cable core is permanently compacted, substantiallyeliminating the interstices between adjacent insulated conductorsthereof, and the well logging cable is thereby made to exhibitessentially no irreversible permanent stretch when subjected to thetensions and temperature cycles encountered in logging a well, whichimprovement comprises the steps of: passing the cable between a payoutmeans and a takeup means under a substantially constant tension lessthan about two-thirds the breaking strength of said cable but sufficientto cause said armor layers to elongate and thereby supply inward radialcompressive forces on said central cable core; heating a portion of thethus-tensioned cable, as it passes bween said payout and said takeupmeans, to a temperature below the melting point of saidethylene-propylene polymer but sufficient to cause saidethylene-propylene polymer to deform under said inward radialcompressive forces and to fill substantially the previously existinginterstices between the insulated conductors of said central cable core;and thereafter, while maintaining said tension and before said heatedportion reaches said takeup means, passing said heated cable portionthrough a cooling trough long enough to reduce the cable temperature toambient conditions.
 5. The method of claim 4 wherein the tension betweenthe payout means and the takeup means is maintained at approximately6,000 pounds.
 6. The method of claim 4 wherein the tensioned cable isheated by passing an electric current through the outer armor layers ofsaid cable as the cable passes from said payout means to a point Cintermediate between said payout means and said takeup means.
 7. Themethod of claim 6 wherein the cable is heated sufficiently to raise thetemperature of the conductor insulation to approximately 250*F.
 8. Themethod of claim 7 wherein the cable is cooled by passing said cablethrough a trough of coolant material located between intermediate pointC and said takeup means and long enough to lower the temperature of theconductor insulation of said cable to approximately 70*F while saidcable moves through said trough.
 9. A well logging cable manufactured bythe method of claim 8.